Air traffic control (ATC) centers are used at most airports to coordinate take-offs, landings, and general aircraft traffic around the airport. Traditionally, a pilot uses a radio to speak to an ATC center to request permission or to receive instructions from the ATC center. With increasing air traffic, it has become difficult for ATC centers and pilots to process all of the oral communications with aircraft without error. Consequently, data link applications have been developed to provide textual communications between pilots and air traffic controllers.
One of these data-link applications, called Controller Pilot Data Link Communication (CPDLC), provides for the direct exchange of text-based messages between a controller and a pilot. The CPDLC application enables the pilot to communicate electronically with an ATC center by guiding the pilot through a series of screen configurations or displays that either elicit flight information from the pilot or notify the pilot regarding flight information. The CPDLC application may be part of a larger flight information/control program or may serve as a stand-alone program.
In current CPDLC systems, when the TTS (Termination Timer, Sender) timer expires for a CPDLC clearance downlink request message, the pilot is informed of the expiration. For example, in a conventional communication management unit (CMU) the status of the message in a message log is changed to EXPIRED. In one implementation, as the status changes, the pilot is given a sidelink message indicating the downlink has expired and that the pilot should resend the request. Upon notification, the pilot will likely want to resend the clearance request and maybe modify the request. However, the pilot has to remember what the previous message stated, or print out the previous message, and then manually re-enter the entire message before resending the message. This substantially increases the aircraft crew workload and head down time, which adds to pilot fatigue and distraction while operating the aircraft. This equally applies to the air traffic controller.